1. Field of the Invention
The present invention relates generally to selector switches and pertains, more specifically, to a selector switch of the type having multiple poles, or contacts, among which connections are made in accordance with the selective positioning of a coded element of the switch.
2. Description of the Prior Art
Conventional selector switches, such as currently available thumbwheel selector switches, employ coded elements which usually include patterns of metallic conductive material carried upon a dielectric substrate for effecting the desired interconnections among the poles of the switch. The patterns are constructed in the form of conventional "printed circuits" in which the coded pattern is etched on a printed circuit board. Usually, the metallic circuit portions are plated with gold to provide an oxide-free contact surface for electrical switching of low level signals, and for low contact resistance. The metallic circuit portions are contacted by electrical contacts which are resiliently biased toward the contact surface. As a result of the conventional techniques employed in the manufacture of the coded elements, the metallic circuit portions usually are raised above the level of the surrounding portions of the dielectric substrate. Thus, relative movement between the coded element and the electrical contacts during selective repositioning of the coded element relative to the electrical contacts requires that the electrical contacts ride over each raised edge of the metallic circuit portions encountered during such movement, resulting in uneven forces required during selection and excessive abrasion and wear on the contact surfaces of the electrical contacts.
In an earlier patent application, Ser. No. 856,728, filed Dec. 1, l977, we describe a selector switch in which a coded element includes a pattern of non-metallic electrically conductive material for effecting the desired interconnections among the various poles of the switch. While that construction offers many advantages, the contact resistance may not be low enough for all installations where selector switches of the same general type otherwise would be useful.
It is an object of the present invention to provide a selector switch in which the selector includes a pattern of electrically conductive material at least a portion of which is a metallic pattern and makes contact with the electrical contacts of the switch, the metallic pattern being at the same elevation as the contiguous dielectric material of the selector at the transition between the metallic pattern and the dielectric material.
Another object of the invention is to provide a selector switch of the type described in which the selector includes a pattern of metallic electrically conductive material integral with a dielectric material, the conductive material and dielectric material being carried in an insert placed in a rotor journalled for rotation among selected positions for effecting the desired interconnections among external circuits connected to the switch, the surface of the electrically conductive material being flush with the surface of the dielectric material in a common contact face.
Still another object of the invention is to provide a selector switch of the type described and in which the selector is constructed of integrally molded first and second parts, the first part being a dielectric synthetic resin material and the second part being a conductive synthetic resin material molded in a pattern configured in accordance with the particular code desired in the coded element of the switch and plated with a metal, such as gold, for relatively low contact resistance and for inhibiting corrosion or oxidation.
Yet another object of the invention is to provide a selector switch of the type described and in which the selector is constructed of a molded dielectric synthetic resin material with a metal member embedded in the dielectric material of the selector, the metal member having a pattern configured in accordance with the particular code desired in the coded element of the switch and a surface flush with the surface of the surrounding dielectric material.
A further object of the invention is to provide a selector switch of the type described and in which the poles, or contacts, are in the form of contact pins having a configuration, dimensions and arrangement suitable for mounting the switch in conventional sockets or receptacles, or directly onto printed circuit boards, to connect the switch to external circuits.
A still further object of the invention is to provide a selector switch of the type described which enables relatively smooth operation and is accurate and reliable and will perform effectively over a long period of use.
Still another object of the invention is to provide a selector switch of the type described which is economical to fabricate utilizing current manufacturing techniques, and is constructed of relatively low-cost materials without sacrificing reliable operation.